Unconventional Natural Resources

ISSN 1650-6553 Nr 288

Mark Wallaker

Mark Wallaker

Uppsala universitet, Institutionen för geovetenskaper

Examensarbete E1, 45 hp i Geofysik

Unconventional Natural Resources

The world has a finite amount of natural resources; coal, oil and natural gas

have fuelled our transport and powered our generators for at least the last 200

years. But as the world’s demand for these commodities increases the supply

itself begins to dwindle, before the age of renewable or nuclear energy fully

begins there will be a period of transition. The fuels for this transition will not

be based on the conventional resources that currently fuel the world.

Instead unconventional natural resources will bridge the gap, these resources are

the focus of this report, while some of the resources covered such as tight gas

have already been used for the last 20 years other like gas hydrates have yet to

be fully researched. While they can be found there is no effective way of

turning hydrates into a useable power source.

Other sources such as shale gas have begun to totally change the energy

landscape of the USA and will begin to do so across the planet with vast

reserves in rapidly expanding and developing countries like China, India and

across South America, as well as help the western world fulfill its demand for

energy while researchers develop efficient and safe ways of harnessing

renewable or nuclear energies. Heavy oil and its derivatives from Canada are

also starting to be pumped around the USA to help them meet their oil product

demands.

Supervisor: Christopher Juhlin

ISSN 1650-6553 Nr 287

Mark Wallaker

Table of Contents

Abstract ... 3

Abbreviations ... 4

1. Introduction ... 5

1.1 The Industrial Revolution ... 5

1.2 Coal ... 5

1.2.1 Basics ... 5

1.2.2 Methods for Locating and Retrieving Coal ... 7

1.2.3 Future Predictions ... 7

1.3 Conventional Oil... 9

1.3.1 Basics ... 9

1.3.2 Methods for Locating and Retrieving Oil ... 10

1.3.3 Future Predictions ... 10

1.4 Conventional Natural Gas... 11

1.4.1 Basics ... 11

1.4.2 Methods for Locating and Retrieving Conventional Gas ... 13

1.4.3 Future Predictions ... 13

1.5 The Future... 13

1.6 Evaluation ... 14

2. Heavy Oil ... 15

2.1 What is it? ... 15

2.2 How do we retrieve it? ... 16

2.3 What do we do with it? ... 17

2.4 Is it a suitable Replacement? ... 19

2.5 Evaluation ... 21

3. Shale Gas ... 22

3.1 What is it? ... 22

3.2 How do we retrieve it? ... 24

3.3 Is it a suitable replacement? ... 26

3.4 Evaluation ... 28

4. Tight Gas ... 29

4.1 What is it? ... 29

4.2 How do we retrieve it? ... 31

4.3 What do we do with it? ... 32

4.4 Is it a suitable replacement? ... 33

5. Gas Hydrates ... 36

5.1 What are they? ... 36

5.2 How are they retrieved? ... 38

5.3 Is it a suitable replacement? ... 41

5.4 Evaluation ... 42

6. Conclusions ... 43

6.1 Short Term ... 43

6.1.1 Short Term Conclusions... 43

6.1.2 Evaluation ... 43

6.2 Medium Term ... 44

6.2.1 Medium Term Conclusions ... 44

6.2.2 Evaluation ... 44

6.3 Long Term Conclusions and Evaluation ... 45

Bibliography ... 46

Appendix 1- Gas Hydrates Around the World ... 51

Appendix 2- Unit Conversion ... 53

Converting cubic feet into tons of oil equivalent (toe) ... 53

Converting cubic meters into tons of oil equivalent (toe) ... 53

Unconventional Natural Resources

Mark Wallaker

Wallaker, M., 2014: Unconventional Natural Resources. Master thesis in Geophysics at Uppsala University 45 ECTS/hp

Abstract

The world has a finite amount of natural resources; coal, oil and natural gas have fuelled our transport and powered our generators for at least the last 200 years. But as the world’s demand for these commodities increases the supply itself begins to dwindle, before the age of renewable or nuclear energy begins fully there will be a period of transition. The fuels for this transition will not be based on the conventional resources that have fuelled the world currently.

Instead unconventional resources will bridge the gap, these resources are the focus of this report, while some of the resources covered such as tight gas have already been used for the last twenty or so years others like gas hydrates have yet to be fully researched. While they can be found there is no efficient way of effectively turning the hydrates into a useable power source.

Other sources such as shale gas have begun to totally change the energy landscape of the USA and will begin to do so across the planet with vast reserves in rapidly expanding and developing economies like China, India and across South America, as well as help the western world to fulfil its demand for energy while researchers develop efficient and safe ways of harnessing renewable or nuclear energies. Heavy oil and it’s derivatives from Canada is also starting to be pumped into the USA to help them meet their demands.

These four resources are known as unconventional due to the novel and unique ways in which they are retrieved from the earth or refined once above ground. They will be used to bridge the gap once the current conventional resources have been used to the point where they are so depleted it is no longer profitable. This report will cover these resources and go into detail about how they found, retrieved and used. It will also cover the predictions for the future of each of these resources. Finally it will give short, medium and long term predictions for the future of these resources and how they will change the world.

Keywords: Unconventional natural resources, Heavy oil, Tight gas, Shale gas, Gas hydrates, Energy

Abbreviations

 API- American Petroleum Institute

 BSR- Bottom simulating reflectors

 CIS- Commonwealth of independent states. Contains: Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Uzbekistan, Turkmenistan and Ukraine.

 cP- centiPascals

 DOE- Department of Energy (USA)

 EIA-Energy Information Administration

 EPA- Environmental Protection Agency

 IEA- International Energy Agency

 JOGMEC- Japan oil, gas and metals national corporation

 LPG- Liquid petroleum gas

 Mtoe- Million tons of oil equivalent

 OECD- Organisation for Economic cooperation and development. Contains: Australia, Austria, Belgium, Canada, Chile, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Japan, Luxembourg, Mexico, Netherlands, New Zealand, Norway, Poland, Portugal, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Turkey, United Kingdom and the United States

 Oil Barrel=159 Litres=42 US Gallons

 SG- Specific Gravity

1. Introduction

The purpose of this report is to describe in detail some of the unconventional natural resources that have either already begun to supply the world with energy or will come to do so in the near future. However to understand our need for energy and what needs replacing first, this introduction chapter will briefly outline the years in which the world changed beyond recognition and begun to rely more and more on fossil fuels. It will also discuss briefly what these fossil fuels are and whether they can still be used as an energy source and for how long they will last. Throughout the report, when required to convert units into Mtoe the method used is shown in appendix 2.

1.1 The Industrial Revolution

The industrial revolution of 1760-1830, which was pivotal in the creation of modern society, was fuelled primarily by two major resources; oil and coal. These resources changed the world into what we see today and still provide us with the majority of our energy supplies. However, this was not always the case and will not be the case in the future. Bookstores could be filled with papers and books on these two resources, but this chapter will briefly outline their histories as well as the methods used to find and retrieve them. It will also touch upon predictions for their future use.

One of the major industries during the industrial revolution was gas and oil lighting. The main source of artificial light before the 1860’s was whale oil, as it produced the purest light of oils available at the time and this led to a huge increase in the demand for these products. Consequently this caused prices to rise dramatically as whales could not be fished quickly enough to supply the required amount of oil. In 1854 an American entrepreneur based in Pennsylvania, George Bissell decided to capitalise on the rising oil prices by separating rock oil (now mainly known as crude) into kerosene which could be used for lighting and was significantly cheaper (Downey, 2009). By the 1870s the oil equivalent of the Californian gold rush had occurred in Pennsylvania, as a cheaper alternative to whale oil, the demand for kerosene was huge so many other enterprising business men and women jumped onto the bandwagon causing the supply to far outstrip the demand and the price of crude oil to plummet. It was not until the early 1900’s with the invention of the Model T Ford when two of the by-products of kerosene, namely gasoline and diesel could be used to power these new machines that the price of oil recovered and began the trend of large and rising oil consumption we still see today.

Another major advancement of the industrial revolution was the significant increase in the mining of coal. New inventions such as the steam engine allowed much quicker removal of the water from coal mines meaning that suddenly, considerably more coal could be mined and used in stationary steam engines for other industries, for instance textile manufacturing and the generation of electricity. Today coal supplies 41% of the world’s electricity as well as 30% of our primary energy needs (World Coal Association, 2013). The following section will include a brief run through of the rise of coal as an energy source and a few of the major factors in the potential decline in coal use over the next 50 years.

In terms of energy sources, the third major advancement during the industrial revolution was that in the gas industry. In 1821 William Hart dug the first well specifically for natural gas in Fredonia just outside New York, after noticing gas bubbles rising to the surface of a nearby creek (Natural Gas Supply Association, 2011). It wasn’t until after World War Two however, that significant pipelines to transport natural gas were built and since then natural gas in many forms has been vital to society. Most of the unconventional resources covered later in this report are a form of natural gas.

1.2 Coal

1.2.1 Basics

William Conybeare and William Phillips (Conybeare & Phillips, 1822). Normally when a plant dies the energy it has stored is released when the plant decays, however during this period the large amounts of peat and swampland meant that the decaying process was interrupted. As this peat was buried under more swampland it became compacted and gases and liquids were forced out from what eventually becomes the coal seam, this led to the deposit becoming more carbon rich. Eventually (over enough time) the deposit becomes coal which can then be dug up and used to run our generators.

There are two main types of coal, these are known as “low rank coals” and “high rank coals”. Table 1 below shows how these are separated and what percentage of the world’s coal resources each are.

Low rank coals 47%

Lignite 17%

Sub-Bituminous 30% High rank coals

53%

Bituminous 52% Anthracite 1%

Low rank coals are mainly used for power generation and have a lower carbon content than hard coals, however they do have a higher moisture content. High rank bituminous coals are used for the manufacture of iron and steel as well as power generation. Whereas anthracite is used for any applications that require a smokeless fuel, such as hand fired stoves or as an ingredient in charcoal briquettes.

In 2012 worldwide coal consumption rose by 2.5%, however the consumption within the OECD declined by 4.2% with the US cutting back most significantly (11.9%). This is due to new regulations of coal fired power plants that limit their effects on the environment. Coal consumption outside the OECD grew by 6.1 % with China accounting for over half of the world’s coal consumption. This is due to the massive requirements the Chinese have to power their ever growing cities (British Petroleum, 2013).

Coal production grew by 2% across the same time with China (3.5%) and Indonesia (9%) producing more to help cope with their demands. At the end of 2012 coal was providing the world with 29.9% of its energy (British Petroleum, 2013). These figures show that while the western world has begun to drastically cut its coal consumption and look towards other sources, the rapidly developing economies towards the east, mainly China and India are having to use coal to fill the demand from their quickly increasing living standards.

Figure 1 shows how coal is distributed across the globe, with the US leading the way with over a quarter of the

Table 1- Table showing types of coal (World Coal Association, 2011)

Figure 1: Graph of the distribution of world coal reserves.

emissions and how this has made coal less cost effective, it is also being diminished by the fact it is the least efficient of the three resources. These remaining reserves will either be left in the ground or extracted and sold to countries that do not have the supply to meet the demand, however this will not be done in the public eye due to the fact the US government will not want to be seen polluting somewhere else for profit.

The USA is also leading the way in the research of clean coal technologies (US News, 2009) however it is almost universally agreed that while the scrubbing of coal allowing it to be burnt with little to no emissions is an option for the future, the process is prohibitively expensive. The US government has been sinking up to 1 billion dollars into research a year in order to find a solution that is versatile enough to be adopted industry wide, however 26 years later they are still no closer (WSJ, 2009). The US are beginning to slow their investment into this field of research which could sound the death knell for coal having along term future within the supply of the worlds energy.

1.2.2 Methods for Locating and Retrieving Coal

Coal has been extracted out of the ground for thousands of years, with the first few thousand years being obviously primitive. Therefore this section will only go into the methods for the locating and retrieving of coal for the last fifty years. This is the period when seismic refraction/reflection has been used to map the subsurface to find coal seams, as opposed to following a seam that has breached the surface.

Coal seams that are mineable are usually located within the top 1.5km of the subsurface, this requires high resolution profiles in order to find relatively thin coal seams (Thomas, 2002). Seismic reflection surveys are often used to serve this purpose as the seismic velocities within coal are usually much lower than surrounding rocks. (Commonly between 1.8 to 2.8 km/s).

Another method used for locating coal seams is the resistivity method, this is because the resistance of coal is much higher than that of the surrounding rock and this allows for the coal to be found quite easily. This method has been used to great effect in India (Verma & Bandyopadhyay, 1983).

There are two main methods for retrieving coal from the earth; surface mining and underground mining. The choice of mining method depends on multiple factors, such as the thickness of the coal seam, the depth to the coal seam and the density of the overlaying ground.

When the coal is close to the surface the coal is usually extracted by open surface mining and there are two main types of open surface mining. The first being open pit mines, these mines are usually dug with vertical levels ever increasing in depth, with the top layer being the widest and the bottom layer the narrowest. This method has a huge effect on the environment both in the harmful chemicals that are left behind and aesthetically with huge pits needing to be rehabilitated back into the surrounding ecosystem. The second open surface method is strip mining; exposing the coal by removing the overlaying material, which is then deposited to one side. The process is then repeated with the waste being used to fill in the space left by the coal seam in the previous section.

When the coal seam is situated deeper into the subsurface, underground mining is used. This involves drilling or digging down to the level that the coal is located and then mining the coal out directly onto some kind of lift to the surface. These methods are now widely automated in order to avoid any accidents, it is however, still used heavily across the globe (World Coal Association, 2012).

1.2.3 Future Predictions

kind and this will inevitably lead to a “push back” on coal from the public, which will have a knock on effect on the world’s political climate. With the public wanting cleaner and less environmentally damaging energy, coal will begin to reduce its share of being one of the world’s main energy supplies and take a back seat to new cleaner energies.

Recently the US government officially defined carbon dioxide as a pollutant (Anon., 2008) and this has forced through congress a change in US energy policy. Coal fired power stations’ main by-product is carbon dioxide, so it is no longer as profitable once the added tax/fines from these emissions are added. The USA also introduced the Waxman-Markey bill (also known as the American Clean Energy and Security Act of 2009). This bill states that by 2025 all coal fired power stations must capture 50% of their carbon based emissions and dispose of them in an environmentally friendly way. It also states that any new coal power plants must capture 65%. These regulations have led to the US moving its focus to nuclear, oil and natural gas for its energy needs. While oil and gas fired power plants still produce carbon dioxide, they are much cleaner burning than their coal counterparts. The normal case with any form of energy policy, is that when the USA changes tack the world follows.

The US EPA in September 2013 announced the first forays into President Obama’s climate action plan, which aims to reduce carbon pollutions from all types of power plants (EPA, 2013). Figure 2 shows the IEA predictions for coal demand from the 4 major users worldwide. The y-axis is in Mtoe which stands for million tons of oil equivalent.

Figure 2 shows the prediction that rapidly developing economies(India, China, Brazil) will have a much greater need for coal to power their generators whereas the USA and the European Union will begin to scale back on their coal consumption.

These developments show that coal still has an important role to play in the supply of the world’s energy. However with the EU and the USA beginning to make steps to reduce their consumption or lessen the impacts on the environment, the rest of the world will eventually be forced to follow suit, meaning that going into the next fifty years coal will become less and less vital for the western world. However coal will continue to be an important resource for the economies in the east, as they look to secure quick and easy energy.

Figure 2- The prediction of coal demand from the 4 major consumers 1990-2020 (Sia Partners, 2013)

1.3 Conventional Oil

1.3.1 Basics

Millions of years ago, the earth looked very different to what it does now, with oceans covering much of what is now land. It is within these oceans that the majority of the oil used to power life as we know it today, was formed. The vegetation and animals that inhabited these oceans absorbed the energy pumped out by the sun and this energy was then stored in the same way it is now, in carbon. After these animals and plants died they sunk to the bottom of the ocean where they were slowly covered with layer upon layer of sediment. As more and more layers were added on top of the remains the pressure on them increased, at the same time the heat also increased. Depending on the heat and depth to which the biomass is buried decides how much oil and/or gas is produced. Figure 3 shows the relationship between the depth and the temperature. Between depths of 1km and 5km and a temperature between 35˚C and 190 ˚C is the window for oil production.

The world’s conventional oil reserves are not evenly distributed, 56% of the reserves are located in the Persian Gulf area of the Middle East as shown in figure 4. This is due to the location of the Tethys Seaway, which existed in the Triassic period around 200 million years ago (The Open university, 2010). This seaway contained large amounts of tropical reef which became the biomass that eventually turned into the oil and gas the Middle East has in abundance today. When this seaway closed, it also produced lots of structural points that became cap rocks for oil and gas reservoirs. The other main reserve of oil and gas is based in North America, with the rest of the world lagging far behind making up for only 28% (Colgate University , 2003).

Figure 3- The relationship between the depth and temperature on oil and gas production- (The Open university, 2010)

1.3.2 Methods for Locating and Retrieving Oil

The massive demand for oil has led to large scale exploration leaving very few stones unturned all in the name of finding more oil. Due to the way oil is formed, some of the reserves are located in the most treacherous locations on earth; harsh deserts and freezing wildernesses’ are just two of such locations.

It is possible to find clues as to the location of oil on both the surface of the earth and from examining the sub surface. Clues on the surface are mainly from the analysis of the rock structure or more clearly from seepages onto the ground or into groundwater. The more important clues, however rely on the imaging of the subsurface. Until the 1920’s the main method for locating oil, was a mixture of luck and guesswork, with most oil companies ignoring geology altogether. The use of a torsion balance changed that view quickly.

While torsion balances had been around for a few hundred years, they were never used to locate oil. In 1924 the first salt dome and oil bearing structure was located using said torsion balance. The salt dome acts as a cap rock and the reservoir rock beneath is much more porous and hence has a lower density.

The next step in gravity measurements was the pendulum method, which used the movement of a tiny pendulum to find the variations in the local gravity due to the rocks below the surface. This method was used to locate large amounts of oil in Texas. Finally this was superseded by the gravimeter which has been constantly refined and is still used today, these can also be used to find oil at sea when they are placed on a ship and used to determine the structures below the ocean floor.

After using a torsion balance further exploration can be used to achieve a greater resolution, seismic reflection can be utilized to do this. Seismic reflection uses the varying seismic velocities within the layers of the earth to map the subsurface and find any potential anomalies or deposits. This method can be very effective when combined with other location methods.

Another method of oil exploration is the utilization of the magnetic method. Most of the non-porous rocks that cap oil are sedimentary and one of the main features of sedimentary rocks is that they are non-magnetic as opposed to igneous or metamorphic rocks which are usually highly magnetic. In 1927 a magnetometer was first used to locate the oil in Yoast Field in Bastrop County, Texas (Texas State Historical Association, 2014).

Before the oil production process can begin there is a long and arduous drilling process to complete. But before anything can begin, permission must be obtained from the land owner (normally the government). Next a structure known as a derrick is erected to support the drill and drill string. The drill string is a length of pipes, which are fastened together and are used to allow power from the top of the well down to the drill bit on the end of the drill itself. As the drill cuts through the rock, a muddy liquid is pumped into the hole. This serves two purposes, the first is to keep the drill bit cool and stop it overheating and the second is to bring the particles of rock back up to the surface so they can be kept out of the way of the drill. It also stops the negative effects of the reaction with gas or fluids that might be encountered during drilling and this leads to a reduction in blowouts. The ground surrounding the well has to be protected from contamination, especially any aquifers. To do this large casings are lowered into the hole and cemented into place, this protects the aquifers but also helps keep the structure of the well safe. Finally, there has to be a rapid and efficient safety procedure, so if any problems are detected the well can be shut down with minimal damage to workers or the environment.

The process detailed above is used for all locations with slight variations for offshore drilling, in that a rig is either floated on the surface and connected to the ocean floor or (if the water is shallow enough) built directly on to the ocean floor with a structure rising to the surface.

1.3.3 Future Predictions

world’s supplies of oil are not infinite as oil takes hundreds of millions of years to form. We clearly cannot wait that long, hence the need for more unconventional alternatives.

It is only a matter of time before new oil fields cease to be discovered and the reserves we have become depleted, meaning that the demand for oil outstrips supply. When this happens the planet will have need of a new method of fueling its cars/planes/boats to mention a few. Be this the unconventional resources discussed in this report or another novel and previously unimagined method only time will tell.

The EIA (US EIA, 2013) stated in their annual energy outlook that the demand for liquid fuels has decreased due to the decline in their use for personal transportation and home heating. This trend will be seen elsewhere across the planet when things such as electric cars and heaters are more efficient and in the case of cars more useable. This will lead to a worldwide decline in the use of oil and this may cause the demand to never outstrip the supply and hence the gap to a new source of energy can be filled without any extra effort. However electric cars are still a long way from fulfilling the needs of most of today’s car owners so there would need to be significant improvements within this field for this scenario to become a reality.

1.4 Conventional Natural Gas

1.4.1 Basics

Conventional natural gas (which for this section will simply be called “natural gas”) that is used in homes and power stations today, is formed in a similar way and at a similar time to the conventional oil that is also used and was described earlier. Hence why they are commonly found together. Looking back to figure 3 which shows how the temperature and depth affect the production of oil and gas, it can be seen clearly that the formation of natural gas follows that of conventional oil, until oil peaks at around 100˚C and at 2800m depth. Whereas natural gas continues to be formed at greater temperatures and to much greater depths, the end of the gas formation window is thought to be significantly over 200˚C and deeper than 5000m.

Table 2 shows the typical composition of natural gas, with a large majority (70-90%) being methane. By the time natural gas reaches your home to warm your house or cook your food it has been refined, to the point where it is essentially pure methane. A chemical known as mercaptan is usually added before the gas is pumped into people’s homes, as this causes the gas to smell and therefore helps in the location of any gas leaks.

Due to its formation being similar to that of oil, the distribution of natural gas is not equal throughout the globe. Once again the Middle East has a large percentage of the world’s reserves. However, for natural gas Russia also has a large share (27%). Figure 6 shows the distribution of the largest and most important natural gas supplies.

Table 2- Composition of natural gas- (Naturalgas.org, 2011)

1.4.2 Methods for Locating and Retrieving Conventional Gas

The last 20/25 years has revolutionized the methods of finding both oil and gas; many of the same techniques used to locate oil which were discussed previously are used to locate natural gas as well. Due to the nature of natural gas formation and its links with the formation of oil they are usually found on top of each other as shown in figure 7, which shows an anticline trap, these formations can sometimes be seen from the surface as certain layers are exposed. These formations are also highly visible in seismic surveys and hence they are used heavily in the location of natural gas.

Natural gas is normally found in two forms beneath the surface, in condensate form and in its gaseous form. Both types are retrieved in a similar way, with a well being dug and cased in a similar way to that of the oil retrieval methods described earlier. Natural gas is lighter than air and therefore separates naturally at the surface. This means that there is no need for large and bulky treatment stages at the surface and instead each well is topped with a wellhead. This is a heavy duty lid, capable of withstanding pressures of up to 20000psi (Naturalgas.org, 2011). This is then topped with a piece of equipment known as a ‘Christmas tree’; a series of cables and tubes that controls and monitors the flow of natural gas out of the well. Once this is installed the gas flows to the surface without assistance and the ‘Christmas tree’ maintains the safest flow rate possible.

1.4.3 Future Predictions

Conventional natural gas supply is in decline in large parts of the world. However, due to the huge increase in unconventional natural gas extraction (which is the one of the main topics in this paper) the reserves of these unconventional sources mean that natural gas as a whole (both conventional and unconventional) is and will remain one of the main sources of energy both in industry as well as in people’s homes.

From an environmental perspective, the fact that when burnt, natural gas produces approximately 50% of the emissions of a coal fired power plant, it is seen as the most important fossil fuel as it will not rapidly increase carbon emissions like coal or oil fired power stations. This is another reason why it is expected to remain an important energy source (NDIA, 2009).

1.5 The Future

earlier. Conventional oil is separated into two distinct sections, gasoline and diesel with their energy contents being 47300 and 44800 kJ/kg respectively, this is significantly higher than coal albeit slightly lower than the final resource in this chapter the methane from natural gas is the most energy filled, with a value of 55530 kJ/kg. This bodes well for the unconventional resources covered later as most of them are based on natural gas (The Engineering Toolbox, 2014).

1.6 Evaluation

Of the three conventional energy sources only one seems a viable option for medium term energy supplies, this is conventional natural gas helped by it having a much greater energy content when burned than the others. However, the conventional form of the natural gas is dwindling and hence new unconventional methods and sources of energy need to be found to fill the gap left by oil and coal. Coal is still abundant within the earth, however the fact that using it produces such devastating environmental effects it will not be a suitable replacement unless giant and improbable leaps are made in coal fired power plant technology.

2. Heavy Oil

2.1 What is it?

In 1980 at the World Petroleum congress in Sydney, the international petroleum community decided they need a universal definition for the differences in crude oil. This led to the separation in classification of the conventional crude oil most commonly used and the unconventional heavy oil, which was labelled “unconventional” due to the unique ways in which it is retrieved from the earth.

Heavy oil is often described as “dead oil” due to the fact it is gas free at reservoir temperature in order for crude oil to be classed as ‘heavy’ then it needs to have a density below 21˚ API (Banerjee, 2012). This measurement is a petroleum specific measurement that is based on the specific gravity (SG) of the substance which is given by the following ratio:

𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐺𝑟𝑎𝑣𝑖𝑡𝑦 =𝜌 𝑠𝑎𝑚𝑝𝑙𝑒_{𝜌 𝑤𝑎𝑡𝑒𝑟} (1)

Where ρ is the density, the API gravity measurement is then given by the following relationship:

𝐴𝑃𝐼 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 =141.5_𝑆𝐺 − 131.5 (2)

Heavy oil was later separated into two distinct types, conventional heavy oil with an API between 21˚ and 10˚ and unconventional extra-heavy oil which has an API of lower than 10˚. There is a further category of extra heavy oil, which is known as bitumen; this has an API similar to that of extra heavy oil. However bitumen differs in its viscosity with extra heavy oil having a viscosity of 1000-10000cP whereas bitumen has a viscosity of above 10000cP. One of the world’s largest bitumen deposits is found in the poorly named “tar sands” of Alberta, Canada which contain no tar, but should probably be renamed oil sands as this is closer to the truth. Apart from the viscosity difference, the properties of extra heavy oil and bitumen are practically identical in their location, retrieval and transport methods. Therefore for the rest of this section they will be referred to as simply bitumen. Bitumen can trace its origins back to the remains of extremely large reserves of conventional oil that was degraded by bacteria in the area that its porous migration took it to. Natural bitumen is often of a very similar form to the residuals left from the light oil refining process (Centre for Energy, 2013).

Bitumen is significantly more viscous than light oil, with light oil being less than 1000cP, this makes retrieval and transportation much more technologically challenging than the conventional oil that can be pumped via pipeline easily. This leads to heavy oil being “upgraded” to a less viscous oil before it is pumped to its destination. This process will be discussed in more detail in a later section.

According to a survey by the World Energy Council (2010) there are 598 known deposits of bitumen across 23 countries, with all of these reported deposits being onshore. Table 3 gives the total amount of deposits for each continent:

Continent Number of Deposits

Africa 9 North America 449 South America 2 Asia 80 Europe 56 Middle East 1 Oceania 1 Total 598

Canada has the largest amount of deposits for any one country (coming in at 231). These bitumen deposits are also considerably larger than any of the others on the planet, table 4 shows that while the USA has a similar amount of deposits it is much smaller in terms of actual bitumen resources.

Country # of deposits Prospective additional resources Total Original Oil Production (millions of barrels) Reserves (millions of barrels) USA 204 37142 53479 24 No data Canada 231 703221 2434221 6400 170400

Table 4 also shows that Canada has already started extracting oil from its reserves both on the surface and below. In the years from 1974 to 2006 Canada has gone from 4% of its oil production being bitumen to 70% marking just how important bitumen is to both their economy and energy needs (Kermode, 2006).

2.2 How do we retrieve it?

Bitumen certainly has a role to play in the future of the world’s energy supply, however currently the profit margin is very small. This has led to most major oil companies being very cautious about investing into this area of the energy industry. The less than desirable profit margins are down to the locations of the bitumen deposits. As the large majority of the world’s reserves are located in harsh, inhospitable areas. America’s reserves are mainly in Alaska where in winter the temperature can drop to an average of -26.5˚C (Travel Alaska, 2014). In Canada the largest bitumen deposits are in Alberta, where the temperature can drop to a similar average temperature to Alaska (-24 ˚C) (Alberta.ca, 2013).

These low temperatures mean that it becomes expensive and challenging to build any pumping or storage stations that can withstand the harsh winters and still be environmentally secure. Bitumen is notoriously difficult to handle and interact with; it also borders on the impossible to conventionally pump natural bitumen through an oil pipeline and requires a large amount of onsite refining before it can be moved. Another major factor in the energy companies’ reluctance to move into this industry on a large scale, is the perception that bitumen is dirty and high in emissions. This will be looked into in more detail in the last section of this report.

Canada is the most successful country that is currently retrieving bitumen from oil sands. Therefore, the retrieval method covered in the rest of this section is the main method used in the Canadian oil industry; this is the Clark hot water extraction process.

The Clark hot water method was first developed in 1920 by Dr Karl Clark but it took until 1967 for Suncor Energy to put it into commercial use. The process is conceptually simple, however it is both energy and time consuming. Firstly, the oil sand is mined and crushed to increase the surface area of the particles. Hot water (50 ˚C to 80 ˚C) is then added to the crushed oil sand. The purpose of this is the water causes the bitumen to become less viscous which in turn causes the sand to separate from the bitumen. If this process was allowed to occur naturally it would take a very long time, however in order to speed up the process the material is mechanically mixed and during this process the larger particles sink to the bottom and can be removed. These excess solids are then normally used to help in the construction of the tailing ponds where the waste is stored later.

After the larger particles have sunk to the bottom air is bubbled into the mixture, this causes the bitumen to collect on the air bubbles and rise to the surface in a product known as ‘bitumen froth’. This froth contains on average 10% solids, 30% water and 60% bitumen. This mixture is not suitable for transporting via pipeline and hence needs more refining. Figure 8 below shows how the bitumen deposits is separated.

The ‘middlings’ is a combination of residual water, solid and chemicals that are added to the mixture, as well as any unrecovered bitumen; these are disposed of in the tailing ponds. These tailing ponds are an extremely controversial environmental topic due to most of them being simply left to contaminate the nearby ecosystems (Us oil sands Inc, 2014).

2.3 What do we do with it?

As described earlier, bitumen froth cannot be transported via conventional pipelines due to the fact it is far too viscous to flow like conventional oil. This leads to the need to upgrade the bitumen retrieved to a less viscous and more conventional oil type substance which can then be piped through already existing pipelines, making the whole process much more cost efficient.

After refining and upgrading, the bitumen becomes known as “synthetic crude” which can then be transported and used for the same things as conventional oil. The upgrading process has two steps; the first is usually a thermal process such as coking and in the second stage the remaining oil from the primary step is processed to make a synthetic crude oil that can be used in most conventional oil refineries. The quality of this synthetic crude depends heavily on the historical process in which the bitumen deposits were formed and therefore not all synthetic crudes are the same.

The first step in the refining process is to separate the lighter more distillable oil from within the bitumen and this is done using a vacuum unit. The lighter portion behaves similarly to the conventional oil that is pumped through most pipelines and equates to around half of each barrel of bitumen. The main challenge in this process is the dealing with the remaining heavier bitumen.

The residual bitumen requires major refining before it can be transported and used, this is done by a cracking process which breaks up the larger molecules and turns the bitumen into a lighter more conventional oil. Bitumen also has a lower hydrogen count than conventional oil; therefore before transportation this must be increased. There are two major cracking processes used within the oil industry; ‘viscosity breaking’ and ‘coking’. Coking also has two methods ‘fluid’ and ‘delayed’ and both of these methods provide a suitable oil to be fed into the hydrogen increasing process which makes them excellent choices for the upgrading of bitumen.

Viscosity breaking, more commonly known as visbreaking, is a process used on heavy oils that reduces the viscosity of the oil making it. The whole process is non catalytic, meaning nothing is added to the oil feed in order to force a reaction and the whole process is reasonably simple. First, the oil is fed into a furnace and heated, then as it is pumped out of the furnace it is ‘quenched’. This process stops the cracking process and is usually done by passing cold oil through the bitumen. This oil is then recovered, cooled again and reused making this section of the process quite efficient. The quenched feed is then passed into a fractionator, which is a tank like machine that utilizes the fact the heavier more viscous substances sink to the bottom, allowing for easy retrieval of each type of gas/oil. Figure 9 shows this process with gas and LPG at the top of the fractionator and the much heavier tar at the bottom. This tar can then be separated using a similar vacuum process as the initial separation of the bitumen leaving heavy gas oil which can be hydrogenated and pumped along pipelines to power plants or for further refining into other oil products (metso, 2001).

The other primary upgrading method, coking, is more commonly used due to the companies operating in the Canadian oil fields being more experienced in this technique. Delayed coking is a process that takes place as each batch of bitumen is passed into a furnace where it is heated and then passed into “coking drums”, these containers provide a suitable environment for the cracking process to occur. This is then fed into a fractionator where it is separated into wet gas and light and heavy gas oil. The remnants at the bottom of the fractionator are then passed back through the furnace and the process is repeated (CB&I, 2012). The heavy oil is then forwarded to the next stage of the process; the increasing of the hydrogen levels.

The other method of coking is known as fluid coking. This process is continuous with the bitumen being pumped through and then moved on, whereas with the delayed coking a batch is pumped around until a desired amount of upgrading has been achieved. In the fluid method, bitumen is preheated and then passed into a furnace, where it is heated to between 510˚C and 540˚C (Bitumen engineering, 2008). This produces the lighter products (around 70%) that can be skimmed from the top and moved into a fractionator and separated in the same way as the visbreaking and delayed coking methods. This also produces the much heavier and more viscous coke, which is fed into a boiler that separates the coke into flue gas. This is sent back to the furnace in order to obtain increased energy retention and net coke, this is then sold as a solid fuel for power generation and is extra popular for cement kilns as these absorb the sulfur emissions emitted when it is burnt. These emissions are the reason this coke is cheaper than most other types of solid fuel (Exxon, 2005).

The second stage in the upgrading process is increasing the hydrogen level of the heavy oil that is left from the primary processes. This process also has the benefits of removing impurities and enhancing the quality of the final product. It is known as ‘catalytic hydro treating’.

The first step within this process is mixing hydrogen with the oil feed and preheating before forcing it under high pressure conditions into a catalytic reactor. This converts the sulfur and nitrogen within the oil into hydrogen sulfide and ammonia, which can be removed reasonably easily. The catalysts that are most commonly used are cobalt-molybdenum and nickel-molybdenum (Elliott, 1990). This process is then repeated in order to finish and stabilize the final product, the liquid feeds from this process are then blended together in order to form the final synthetic crude oil that is pumped to power plants or other final locations.

2.4 Is it a suitable Replacement?

The first part of this section discussed the world’s bitumen reserves and pointed out that while there is a lot of it, there is not enough on the planet for bitumen and other heavy oils to be considered a complete replacement for conventional oil and gas. It is however a good supplement to these resources and it will fill the gap as conventional reserves begin to dwindle. Bitumen has the added bonus that once it has been refined it can be transported and used by an infrastructure that is already in place.

One major drawback is the environmental effects that bitumen mining and refining has on the land around the mines. This will be a major drawback for the heavy oil industry as the world progresses towards cleaner and less environmentally damaging fuels.

Figure 10 shows that the currently producing oil fields output will decline significantly in the next 20 years, meaning that something has to fill the gap. This diagram shows undeveloped oil fields as being the supplementary production to current conventional resources with non-conventional oil and the liquid form of natural gas only contributing a small amount, however if this is not the case and these oil fields are not completed or the estimates have been exaggerated then heavy oil can fill this deficit. Figure 11 below is based on a report by the US geological survey (Meyer & Attanasi, 2013); it reported that over half of the world’s oil reserves are composed of bitumen or heavy oil. If all of these reserves are recovered in an energy efficient way then they have the potential to replace conventional oil reserves completely. The problem is that it takes a significant amount of energy to upgrade and refine bitumen and heavy oil, to a point where it can be used by the current conventional oil infrastructure.

There is however a huge drawback to bitumen and heavy oil which may prove to be its undoing as a major energy source, the effects on the environment surrounding the mining and upgrading of bitumen is huge. The tailings ponds where the waste water from the initial bitumen extraction is stored are a major problem and a rightly controversial aspect of the whole process.

These tailings ponds are generally composed of the byproducts of the extraction process, so are full of water, sands, silt, clay and residual bitumen. This waste is held in a series of ponds and this water leaks out into the surrounding ecosystems causing damage to both plant and animal life. There is also the danger of the leaks breaching an aquifer or finding their way into a stream, causing harmful pollutants to spread far more rapidly than they would otherwise.

Another source of pollution is the reactors and furnaces where the coking and hydro-treating takes place. The heating of the bitumen causes pollutants, such as a variety of hydrocarbons which are a known cause of climate change and global warming (Hydrocarbon Processing, 2011). The contaminants from these furnaces however are the lesser of the two pollutants. A recent study (Wania & Parajulee, 2014) claimed that roughly 2/3rds of the pollutants at the Athabasca oil plants came from the tailings ponds rather than the furnaces. Tailings ponds are designed to be naturally reclaimed by the earth, however it takes around 30-40 years for the silt, sand and clay on the bottom to settle and become part of the local ecosystem. This however has only happened to one tailings pond since the Canadian oil industry started using them (Oil sands today, 2010). A worrying sign for this concept is that only one of these tailings ponds has been completely recovered by the environment since these ponds were first used.

These tailings ponds also devastate local birdlife, as the birds cannot tell that the water they are about to land on and drink from is extremely toxic, this is a highly controversial topic around bitumen production and has led to the companies operating there to develop systems to scare birds away. These range from effigies of humans to radar and laser systems that detect and scare birds away. However these are not 100% effective and the tailings ponds require extra environmental consideration. (Golder Associates, 2009) A series of patents have been filed in the last few years that allow for the recovery of these tailings ponds to complete quicker than if they are just left for Mother Nature to fix.

Heavy oil once split into its 3 main products, gasoline, diesel and heavy oil it has 3 different energy values. The first two (gasoline and diesel) are the same as the conventional resources discussed in the first chapter (47300 and

32%

21% 47%

World Oil Resources

Recoverable Natural Bitumen (95161.5 MToe)

Recoverable Heavy oil (63441 MToe) Conventional oil (139160.9 MToe)

44800 kJ/kg). Heavy oil has a slightly lower energy content to these two products being only 43000 kJ/kg. This puts heavy oil at nearly double the energy content of coal which goes someway to making up for the environmental concerns, of both the retrieving and refining of bitumen (The Engineering Toolbox, 2014).

2.5 Evaluation

While the facts outlined in this chapter point out that there is potential to use heavy oil as supplement to conventional fossil fuels it has significant environmental effects both in the retrieving and refining of the bitumen. Due to these environmental concerns heavy oil will never fully be used as an energy source as the effect on the environment is too detrimental and environmentalists would never allow it. However, when desperate for energy, it will be the economy which will force the use of heavy oil in large quantities with the environment being collateral damage. Heavy oil and bitumen can be used as a filler to keep the energy supply stable, while developments in cleaner, greener energy can continue to the point where they are suitable to take over from fossil fuels as a whole.

3. Shale Gas

3.1 What is it?

Shale gas is the current press buzzword when it comes to new sources of energy or any environmental concerns. However they seem to talk about it a lot without ever really saying anything. This chapter will go through the topic in much more detail.

Shale gas has already began to fulfill its potential in the US with their government claiming it no longer needs to import any natural gas to fulfill its energy needs. Other countries will soon follow in the USA’s footsteps and unleash their own shale gas reserves.

The reason shale gas is known to the world as shale gas is simple, within shales buried deep under the earth, gas has become trapped and turned these shales from rocks of no interest into s for a huge energy source. Figure 12 shows a schematic of natural gas resources in general, however this chapter focuses on the gas rich shale band at the deepest part of the diagram.

The knowledge that these shales could potentially hold gas reserves was not unknown to oil and gas companies, it was first discovered in 1821 (Rao, 2012) however the technology to retrieve it was not created until the 1950’s and even then it was not profitable. It was in 2000 that shale gas finally reached the 1% mark of the USA’s natural gas supply, although this has increased exponentially since.

The total amount of world shale resources is essentially unknown, as every year the amount of recoverable resources increases, the EIA produces a yearly report into world shale gas. Table 5 shows the table lifted from the 2013 report (EIA, 2013). It shows how the shale gas resources have grown by 677 trillion cubic feet (159095 Mtoe) in the two years between the reports and this is an increase of 10.2%. The number of both basins and formations have also doubled as more and more countries look into their own reserves after seeing how the US has benefited.

This report also states how they estimate 10% of the world’s total oil and gas energy reserves (not including gas hydrates which make up the final chapter in this report as they are currently not efficiently recoverable.) This 10% is a considerable amount considering how skewed the distribution of conventional oil and gas is spread, with the majority being in the Middle East. Shale gas does not suffer from this, as it is spread throughout the planet, with large reserves in emerging economies in South America as well as North Africa and extremely large deposits in Central Russia. Figure 13 shows a map of the world with shale resources overlaid. The red groups have been thoroughly studied and there is an estimate for the amount of recoverable gas, the peach coloured groups have been found, however there is no current resource estimate. It can also be seen that China has resources covering nearly a third of the country, this may prove a huge benefit as their population continues to consume more and more fossil fuels.

Table 5- Table showing the comparison between EIA’s 2011 and 2013 shale gas reports. Shale gas resources in Mtoe: 2011-158928 and 2013- 175176.

(EIA, 2013)

Shale gas has already changed America’s outlook on energy supplies and it clearly has the potential to drastically alter the rest of the world’s supplies as well. However the technique used to recover shale gas, is highly controversial due to various environmental concerns, as well as uneducated press reports causing a backlash from the general public. The next section will look at the method known as hydro-fracturing, looking into both its merits and its pitfalls.

3.2 How do we retrieve it?

Hydraulic-Fracturing or ‘fracking’ as it is more commonly known, is not a new technique, it has been used in a way, since the start of the petroleum industry. It is incredibly useful for clearing blockages and debris from normal oil wells, water wells or pipelines. The simple idea behind this type of fracturing is that by putting enough pressure on the blockage, the blockage will be blown away or into pieces. The process of non-hydraulic fracturing is even older, it has been used to split granite and other rocks for centuries.

Towards the end of the 1980’s the oil industry began to perfect directional drilling, making it accurate enough to drill along a slanted or horizontal oil deposit. In 1997 helped by an advance in hydraulic fracturing now known as slick water fracturing, the first economical well was completed in Texas. Slick water fracturing is called as such because of the use of different chemicals within the water that is used in the fracking process.

Fracking in shales itself is a simple operation, firstly the well is dug down to the depth required, then the well is turned horizontal (or to the required angle) and drilling continues through the source rock. This is much more efficient that a conventional (vertical drilled) well as it allows for much more of the source rock to be reached. It is also possible to further increase the production from a gas field by having multiple horizontal wells, which increases the flow rate of the gas out of the ground. Figure 14 shows this concept.

Once the well has been dug along the source rock, the fracturing can begin. This is the process of pumping a mixture of chemicals, water and sand into the well at high pressure, this is then forced out of purposefully placed holes in the well casing, fracturing the surrounding shale. This can also be seen from figure 14. After a successful fracture the water and chemicals are pumped out of the well allowing the gas to flow from the shale up the pipe to the surface. The sand that was also pumped through the well is used to prop open the fractures allowing them to remain open and the gas to continue to flow, this concept is shown in in figure 15.

The mixture pumped into the well to commence fracking is the foremost controversial topic when it comes to shale gas. Although the mixture is 90% water and 9.5% sand, the remaining .5% is the cause of the controversy. This remaining percentage is made up of a collection of chemicals that are used in everyday life, however they are not particularly welcome beneath the surface. Table 6 below shows the most common chemicals and what they are normally used for.

Sodium Chloride More commonly found in table salt.

Ethylene Glycol Used in many household cleaning fluids.

Borate Salts Used in the production of lipstick.

Sodium carbonate An ingredient in washing detergent.

Guar gum Used in the making of ice cream and sweets.

Isopropanol Used in deodorants.

The environmental consequences if these chemicals leaked into an aquifer or into the water table would be devastating, they would destroy wildlife as well as the ecosystem around them. This is why it is so important for these chemicals to be heavily regulated, knowing what is being pumped into the ground and what remains once it has been pumped out is an easy way of finding out what chemicals remain beneath the surface. The bonus of the shales being so deep is that the chances of the chemicals, if leaked, making it to the water table are slim, however the gas industry has to make sure that they are doing everything in their power to avoid these leaks.

Another issue with the fracking process is induced seismicity, this also is a result of the fluid used, but not in the same way. When fracking began to be commercially available in the US there were reports of companies disposing of the fluid retrieved from the surface in nefarious ways. Rather than take the waste water to a treatment plant and alter it back to a safe or reusable state, companies were injecting the waste fluid back into the earth at another location. This led to a dramatic increase in earthquakes due to the inevitable increase in pore fluid pressure (Horton, 2012). This also led to a backlash from various environmental and political groups and there are now calls for hydraulic fracturing to be included in the rules laid out by the US government’s energy policy act of 2005

Figure 15-Close up view of a shale fracture. (PROPublica, 2013)

(US Government, 2005) which discussed the use and regulation of wells dug near aquifers as well as the disposal of liquid waste.

This induced seismicity from the fracturing itself is easily monitored, by drilling boreholes close to the well and inserting seismometers within. This allows for regular checks for micro seismic events within the fracking zone, figure 16 shows a schematic for this. To this day there have only been three reported shale gas fields that have experienced seismic events as a direct result of hydraulic fracturing and the highest recorded magnitude was 3.8. This is only one of four earthquakes that have been felt by humans as a result of hydraulic fracturing (Durham Energy Institute, 2013)

These two extra environmental concerns need to be properly regulated in order for shale gas to fulfill its potential in the rest of the world, like it is beginning to in the US. In order for the public to agree with the concepts, the press need to also begin releasing less biased and sensationalist headlines. The last section in this chapter will continue to discuss whether shale gas is a worthy replacement for current conventional fuels.

3.3 Is it a suitable replacement?

As the USA has seen, shale gas is already coming to the fore as a viable alternative for oil and is beginning to completely replace the conventional gas that the USA used to use. This is helped hugely by the fact that once the gas has been extracted from the shale it is no longer unconventional and can be transported and burned in the same way as conventional gas. This means that there is no need for new infrastructure to be built which in turn raises the profit margins on the gas. It does however mean that shale gas still suffers from the same environmental concerns as conventional natural gas when it is burned for energy. These concerns also need to be addressed with more advanced technology if shale gas is to continue in its rise in importance. The EIA predicts that by 2040 roughly 50% of the USA’s gas production will be in the form of shale gas as shown in figure 17. Figure 17 also shows how the contributions from tight gas stay at a similar level in the next 25 years and this is discussed in the next chapter.

The amount of shale gas predicted to make up this 50% ranges from 9.7 trillion cubic feet to over 20 trillion cubic feet (EIA, 2013). This large range in values is due in part to the fact that the US government is not 100% sure of

There is enough shale gas around the world (as shown at the start of this chapter) to completely change the world’s energy landscape. Countries that previously had to import large amounts of their gas to meet their energy needs no longer have to, if they can capitalize on the shale gas beneath their soil. Emerging economies in South America can potentially utilize the boom from exploiting their resources to help propel them to the upper echelons of world power. No longer will Russia have near total domination of the European gas trade, which they have used as a political weapon in the past. In order to see their wishes fulfilled they have cut off gas to Europe leading to huge natural gas shortfalls, this however will no longer be effective (Kramer, 2009).

Shale gas once above ground, is very similar to the conventional natural gas mentioned in the first chapter and also mainly methane. This means that its energy content is the same (55530 kJ/kg) this makes it the most energy filled of all the natural resources studied in this report. It does also mean that it suffers from the same environmental drawbacks as conventional natural gas when burned.

In order for shale gas to fulfill this clear potential, the governments in charge must ensure strict regulations are created and adhered to, avoiding any form of major natural disaster is a necessity as always, but with shale gas the public quickly changes its opinion as can be discovered by the number of ‘fracking is bad for our bodies’ or ’frack off’ type protests that continue in almost any country that has shown an interest in shale gas, especially the UK and US (Extreme Energy Action Network, 2014), (Silverstein, Jason, 2013). Once again the needs of the many will outweigh the desires of a vocal minority and shale gas will play a huge part in the future of the world’s energy supply.

3.4 Evaluation

A problem with having such an abundant resource across the planet is that the world may slow its investment and research into renewable energies or a previously unheard of and unique technique for generating power. This must not happen as shale gas is still a fossil fuel, it is not infinite like the wind and will run out one day. As a planet we need to ensure that when it does happen we have a suitable, efficient and cheap replacement.

4. Tight Gas

4.1 What is it?

Tight gas is the second of the unconventional natural gas resources that is covered within this report and while it is similar to the shale gas that has been discussed in the previous chapter, it warrants its own section due to the differences in reservoir rock and retrieval methods. Tight gas reservoirs are found mainly within low permeability sandstones. During the 1970’s the US government penned a definition for tight gas reservoirs, this was that the gas flow permeability had to be less than 0.1 milliDarcy (mD) or 9.869x10-13 _m2 _{(Holditch, 2006). This however}

was not so much a scientific measurement but rather a political one, as differing amounts of tax credits and rebates were awarded depending on what type of reservoir was being processed.

The scientific definition of a tight gas is more complex, however the definition is still based on the flow rate of the gas. A significant problem with defining tight gas reservoirs is that they only flow when artificially stimulated, this is done by a form of hydro-fracturing. The flow rate is given by equation (3) below:

𝑞 = 𝑘ℎ(𝑝 − 𝑝𝑤𝑓) 141.2𝛽µ[ln (𝑟𝑒 𝑟𝑤) − 0.75 + 𝑠] (3) Where: q Flow rate k Permeability h Thickness

p Average reservoir pressure

pwf Flowing pressure

β and µ Fluid properties

re Drainage area

rw Wellbore radius

s Skin Factor

These different factors mean that creating a general permeability value for any form of tight gas is not ideal. At great depths, there is a much higher pressure on the reservoir which leads to an increased flow rate and allows for total completion of the well. Alternatively the reservoir can be shallow and the flow rate will be much lower and may not be possible to totally complete the well (SPE International, 2013).

Once again, the largest portion of world reserves is in the US and Canada and this has led to a similar situation as with the oil sands in Alberta where the world leaders in tight gas retrieval are based in North America. Tight gas has already begun to contribute significantly to the world’s natural gas production. Figure 19 shows how tight gas (labelled tight sands in the diagram) has been the biggest unconventional contributor for at least the last 20 years (if the prediction is presumed to be true). Looking beyond this graph, the future will lead to greater recovery technology and discovery which will lead to an even greater proportion of resources coming from tight gas.

Figure (19) - The current and predicted natural gas production (Total, 2006) Figure (18) - The distribution of tight gas reserves in Mtoe

Figure from (Total, 2006)

4576.2 Mtoe

2881.3 Mtoe

1186.4 Mtoe

17287.8 Mtoe

Tight gas has been a useful and valuable commodity for the world’s energy supplies already. The technologies put in place to retrieve the gas from the silts and sandstones are already established and are covered in the next section.

4.2 How do we retrieve it?

Retrieving tight gas from the sandstones and silts in which it is trapped and stored is possible with two different methods. Where the sandstone is a solid formation across a section of the earth it is possible to extract the gas using the hydro-fracturing method described in the previous shale gas chapter.

The other method, is known as “acidizing”, which is similar in concept to hydro fracturing but uses acids to dissolve the sediments and other materials rather than hydraulic pressure. These fractures increase the size of the pores, stimulating the gas within and allowing the gas to flow out and be caught at the surface.

As hydro-fracturing has been extensively covered in the shale gas chapter earlier, it will not be gone into in this section in order to avoid repetition. The only difference between the shale gas extraction and tight gas extraction is the reservoir rock that is fractured in order to stimulate the gas. Acidizing however, will be covered extensively within this section as it is more commonly used in the extraction of tight gas.

Acidizing or ‘acid fracturing’ utilizes the same concepts as hydraulic fracturing in the sense that, in order for the gas to be released from the pores within the reservoir rock, the pores of the reservoir rock need to be stimulated in such a way that the gas can flow out and up the well pipe. Whereas in hydraulic fracturing a concoction of high pressure water and a collection of chemicals are used. In acidizing, different acids are used, the acids used depend on the composition of the reservoir rock (Schlumberger, 2014).

The most common type of acid used during an acidizing treatment is hydrochloric acid, as it dissolves limestones and other carbonate collections within the reservoir rock. If there is a large amount of quartz, sand or clay however, a mixture known as “mud acid” is used to dissolve these materials (anon, 2014). Mud acid is simply a mixture of hydrofluoric and hydrochloric acids. In addition to these acids, sometimes there are other substances added into the mix. These are used for a variety of reasons, for example, corrosion inhibitors which slow down the effect of the acid on the well casing. Suspending agents are also added, these cause minuscule blockages within the fractures allowing them to stay open. Alcohol is also added as an accelerator for well clean-up. (Rig-Zone, 2014) The first step in this process is the drilling of the well along the reservoir rock, this may be a vertical seam or a horizontal one. The same technology that has allowed hydraulic fracturing to become the method of choice for the retrieval of shale gas, horizontal drilling, has allowed for the much easier retrieval of tight gas as well. Figure 20 below shows how this horizontal drilling allows for a much greater part of the reservoir rock to be affected by the acid fracturing process.